Dendroclimatologists Answer Back

This thread is dedicated to dendroclimatologists who are seeking for a way to answer alleged “misinformation” at climateaudit without having to defend themselves against dozens of follow-up posts. Any posts on this thread from non-dendroclimatologists seeking to argue or contest these comments will be deleted, although posters, including myself, will be free to discuss these pearls on other threads. Given the allegations against us, I’m sure that this will be the most active thread in our history.

Or maybe you just want to give information on site selection or resolving mixed temperature and precipitation signals in the tree ring data. Over to you, dendroclimatologists.


  1. Mark H
    Posted Mar 30, 2007 at 10:06 AM | Permalink

    As a curious lay person and long-time lurker, I usually just read and try to understand the science. I hope Steve’s good faith offer is accepted and some of more complex dendo processes are elaborated upon.

  2. Kristen Byrnes
    Posted Mar 30, 2007 at 11:29 AM | Permalink

    I think what Mr. McIntyre is offering is the right thing to do.
    I think that it would be a good learning experience for everyone if the dendrochronologists would demonstrate any mistakes he may have made and allow him to make any corrections that should be made.

    Steve: Kristen, welcome here. Kristen is a high school student whose thoughtful website was brought to our attention by Paul here

    I’ve transferred all messages other than two above, including some nice comments about Kristen’s website, to another thread as this thread is to be reserved for dendroclimatologist comments WITHOUT repartee by other commenters here (who are, of course, welcome on other threads.)

  3. bump
    Posted Apr 1, 2007 at 3:16 PM | Permalink

    bump 3

  4. bump
    Posted Apr 2, 2007 at 7:19 AM | Permalink

    bump 4

  5. Rob Wilson
    Posted Apr 2, 2007 at 7:46 AM | Permalink

    Dear All,
    below is a response from a friend and colleague who would like to remain anonymous.
    don’t shoot the messenger, but I agree with everything said.

    My response to this post is that I think you will get few, if any, responses from dendroclimatologists – for what I’ll call ‘sociological’ reasons rather than scientific reasons. Underscoring my hypothesis are the responses to Peter Brown’s post. If any of you knew Peter, you’d know that he is an honest, sincere and hard-working scientist, like Rob Wilson. Yet, the majority of responses to Peter and Rob are so accusatory [or worse] that it is completely a waste of their time to bother corresponding on this site. Only a small portion of what is happening here is of academic or scientific value.

    I’ve read this blog for ~6 months now and have been offended by the discourse and personal attacks against many of the scientists discussed. What is most offensive is that few, if any, of the readers here know: 1) how hard-working most of the scientists slammed are, 2) the difficulties of academia [for example, NSF funding rates in paleoclimatology have dropped from somewhere near 20% in the 1980s to nearly 5% in recent years, despite an increase in the number of scientists in the field. On top of this, there are more stringent requirements about reporting preliminary results related, etc. these days; and this does not include the need for and competitive nature required to publish a new finding or idea. Free time is evaporating in the life of academics; most of the people you talk about work 6+ days/week and sleep much less than they should.], and 3) many of the scientists who are accused of being on ‘the team’ do not get along as well as is assumed here: many have extremely competitive personalities. To think that this science and its results is a collusion is a delusion. The discussion of people on this blog is uncivil and uninformed.

    Why would anyone come here to defend their methods when the same battles are occurring within the science? There are many other time-consuming tasks to deal with on a day-to-day basis within the science that super cede posting here. Several, of the top scientists in dendro do not even subscribe [or rarely post] to the dendro listserv because they do not have the time.

    The science is self-corrective as all science is. There has been some significant improvement in methods over the last 20 yrs. Is it complete? Nope. But which science is?

    And, finally Steve M, though you are more civil than most here, you cherry-pick pretty well in making your arguments. One case in point – the quotes you copied from the discussion on the dendro listserv. A second case in point is the broad ‘Project for the Dendro Truth Squad’ stone you hurled up on this page. Those in the know, who really know the science, know not to use that chronology and know who still use that chronology. The work that uses that chronology for a temperature reconstruction is less-respected than others. Please, do not cast the whole field as deceitful or ignorant of this. You state that it is not your intention to slander the whole science, but why post the picture of that tree and make road statements, make a separate post about it and string a long list of papers that use that chronology if you are not trying to undermine the science? Why not post the longer string of papers that DO NOT use that one site? The final point, you and others are beating some extremely dead horses. The people and papers you ‘audit’ is very selective. You ignore more recent work that surpasses others.

    I know this post is futile, but I had to write it. Tear away.

  6. Steve McIntyre
    Posted Apr 2, 2007 at 9:31 AM | Permalink

    Those in the know, who really know the science, know not to use that chronology and know who still use that chronology. The work that uses that chronology for a temperature reconstruction is less-respected than others. Please, do not cast the whole field as deceitful or ignorant of this.

    If you say that the work that uses Qilianshan junipers as a temperature proxy is “less-respected” than others, then I presume that such work should not be relied upon in IPCC 4AR or that appropriate asterisks should be placed in IPCC 4AR. I listed the following studies that used Qilianshan junipers directly or indirectly: Crowley and Lowery 2000, Mann and Jones 2003, Moberg et al 2005, Hegerl et al 2006, Osborn and Briffa 2006. All of these studies are cited favorably in IPCC 4AR. I did not comment on the motives of the IPCC 4AR authors, but, if, as you say, these studies are “less-respected”, that should have been mentioned in an assessment report.

    Why not post the longer string of papers that DO NOT use that one site?

    OK, here are papers covering the MWP cited in IPCC AR4 that do not use Qilianshan junipers directly or indirectly? Jones et al 1998; MBH99; Briffa 2000; Esper et al 2002/Cook et al 2004 (which use the same proxies); and D’Arrigo et al 2006. Both lists are the same length.

    Briffa et al 2001 and Rutherford et al 2005 go back only to 1400 and Rutherford et al 2005 is simply a re-working of MBH/Briffa 2001 proxies.

    I did not suggest that using Qilian junipers was by any means the worst sin of these studies – only that, if dendrochronologists are taking time to observe that Meko’s Alberta white spruce are precipitation proxies, they might have taken a little time to submit a comment to one of the journals on the use of Qilianshan junipers for any one of the multiproxy studies listed above. While those in the “know” may be aware of the problem of these proxies, I am unaware of any published record of these concerns. IPCC must deal with the published record and so the failure to record these concerns distorts the public record.

    I’ve obviously pointed out many other problems with the non-Qilianshan-using studies that are much more serious. For example, the continued use of Mann’s North American PC1, long after defects in its calculation were reported. It’s bad enough that it was used in MBH99 and Mann and Jones 2003, but its use has seemingly accelerated after problems became known – being used in recent studies Rutherford et al 2005, Hegerl et al 2006, Osborn and Briffa 2006 and the Juckes et al submission. I’ve never tried to attribute a motive to its continued use, much less whether such continued use was “dishonest” or “ignorant”. But it sure is hard to think up a valid reason for its continued use, leaving one to speculate as to motives.

    In addition to their use in Mann’s PC1, bristlecones/foxtails, which were known to be problematic long before the NAS Panel and which the NAS Panel said should be “avoided”, are used directly in Crowley and Lowery 2000, Esper et al 2002, Cook et al 2004, Moberg et al 2005, Osborn and Briffa 2006 (additional to use of Mann’s PC1), Hegerl et al 2006 (additional to Mann’s PC1) and in the Juckes submission.

    This leaves two studies: Briffa 2000 and D’Arrigo et al 2006 – which in its medieval portion – has virtually identical proxy selection to Briffa 2000. As I’ve observed previously, the medieval-modern relationship in these two studies is not “robust” to use of the Polar Urals Update instead of Briffa’s Yamal chronology. I remain very dissatisfied both with this lack of robustness and the failure of the various authors to explicitly address it. These studies also have the “divergence” problem and their attempt to make conclusions about medieval-modern relationships without resolving this fail totally in my opinion. The NAS Panel was very concerned about this issue in their hearings and, while the NAS Report is evasive on the divergence problem, some of the members continue to be dissatisfied with the use of dendro reconstructions without a resolution of this matter.

  7. Steve McIntyre
    Posted Apr 3, 2007 at 6:38 AM | Permalink

    I’ve transferred some posts from non-dendroclimatologists to here .

    I’m going to cross-post some comments from dendro folks made on other threads as I notice them. Martin Wilmking posted the following from another thread here. I responded on the other thread here. Wilmking’s work was discussed some time ago in the two threads Wilmking in Alaska, Positive and Negative Responders while upside-down quadratics were previosuly discussed, inter alia, at Twisted Tree Heartrot Hill and bender on Gaspe .

    martin wilmking says:
    April 3rd, 2007 at 12:14 am

    Dear all,

    i would like to strengthen the problem, that it is quite difficult to keep up wit hseveral posts runnng at quite some speed. e.g. a colleague emailed me this morning about this one, and i have been only scanning most of the replys. i will take more time to read them all in detail.

    some things concerning the neg and pos responders:

    after we stumbld across that fact, we tried to find an explanantion and found some type of threshold response, meaning individual trees were complacent to temperature and after temperature indices crossed soem value, growth started to either increase or decrease (GCB, 2004). rosanne d’arrigo found similar phenomenons in her TTHH site in canada. in that paper they proposed to use the “inverted U shape” function, as i recall. i dont have the paper right in front of me.
    since we also asked ourselves what this divergence phenomenon means for dendroclimatic reconstrcution, we did two things: looked at other sites around the circumpolar north and found something similar (wilmking et al GRL 2005), and looked for site specific issues (wilmking and juday, global plan change ). there we found that most trees (up to 90 %) in northwestern alaska still responded positively with increasing temps, while in northcentral AK, responses were more mixed, and in northeast AK, most trees responded negatively to increasing temps. there is also a precip gradient along that transect and we hypothesized that trees in the west can still benefit from warming, since they have enough water to growth, whereas trees in the east might become more drought stressed. the new paper by pisaric et al. extends that transect further east and finds similar responses (75% neg on average there,we had in our easternmost sites about 70-80% neg).
    sooooooo, once we had cored the trees, thought about it, submitted the papers, did the correction, got them accepted, we are still unclear why this is happening.
    it takes some time. and in my though process it is actuall helpful to scan all your replies to get some additional ideas. more later, have to run….

    martin wilmking says:
    April 3rd, 2007 at 1:03 am

    ok, back at the computer

    some general ideas are:

    the limiting factor is shifting. from temperature to moisture. this could be a completely new phenomenon due to some unprecedented environmental “stresses”.

    it could also be a normal phenomenon, where a species adapts to new environmental conditions. some individuals are better suited to cope with it and survice, others do not. that might mean that ring width could be used as a proxy for temperature in a limited range of environmental conditions only. however, other factors, such as a widespread divergence of growth trends in populations of trees could be indicative of a situation where the environmental conditions e.g. change quite fast, and the result is decline or death of some parts of the population.

    that might be testable, i.e. we would need to look at a similar period (MWP) to see if similar phenomena occured. problem is of course to find enough samples.

    so, while we accept this phenomenon as challenging, we do not think it devalues dendroclimatology. rather, we are asking the questions: how widespread is this? how to deal with this issue? what consequences might it have? how can we make use of this phenomenon to a) learn about the ecology of trees, b) study the ecological interactions of trees with environmental parameters and incorporate this new knowledge into our scientific thinking. it is a slow process, but it is ongoing.


  8. Steve McIntyre
    Posted Apr 3, 2007 at 6:50 AM | Permalink

    I’ve collated some comments from Peter Brown on other threads. You can consult the relevant threads for the dialogue if you wish.

    Mr. McIntyre-
    What the hey, I’ll bite since my name has come up in your discussion. First, on archiving, most of my current research is involved in fire history reconstructions, not dendroclimatology. Check out archived data sets on the International Multiproxy Paleofire Database ( I archive my data sets as soon as they are published; however, I do not dismiss others who do not. Each has his or her own reasons for when and, in fact, if they do so. As far as ecological or climatological data sets go, as a discipline dendrochronology was long ago ahead of the curve with the ITRDB. Second, as for our chronologies that we collected several years ago to look at temperature response in the nothern Rockies most are from 5-needled pine spp (whitebark and limber) and to be quite honest do have a mixed temperature and precipitation response in them. Others are from Engelmann spruce and show the divergence problem seen in upper latitude sites. We have both ring width and density chronologies, and we are still exploring ways that we can refine the climate signal in these data – from mechanistic, statistical, and simulation modeling approaches. There is no hidden agenda.

    Finally: I have little patience for your blog. You only picked out the above quote of mine from the ITRDB thread of the other day, but here is the part right before that:

    I have to admit I am a lurker on CA, and while some of those that comment there appear to be quite sensible (in fact often have some good points) most are in the realm of far-out absolute deniers of anything that smacks of global warming. It’s completely analogous to Henri’s description of dealing with the creationists; they’ll seize upon the slightest uncertainty to tear down the entire discipline.

    Ad hominen attacks invariably arise for anyone who attempts to offer an alternative view to the preconceived notion of the moment. Typically a thread here quickly devolves from anything remotely connected to science into a personal attack. And that is no way to try to carry on a conversation (if that is the goal).
    Peter Brown
    Mar 31, 4:33 PM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    Mark T:
    It only becomes an ad-hominem when the attack is used to cast doubt on the person’s argument.

    Thank you for helping me make my case; ad hominem is when one attacks “an opponent’s character, rather than answering his argument’? (Webster’s). I made an observation about what I perceive as a general tone of much of the discussion on this blog: you manage to insult me by calling me a hypocrite in one of the very next posts. You have no basis for questioning my dealings with any of my colleagues, yet you resort to calling me names.

    I am growing very tired of the prevarications thrown out to justify withholding the data used in support of a study’s conclusions.

    John Norris:
    Organizations are most productive and most respected when they are successfully self- policed. Had MBH been fully expected to proactively archive data by their dendro peers, a great deal of dendro credibility would have been saved.

    John Baltutis:
    However, why don’t you dismiss those who don’t follow standard practice? Don’t you care or is it that you’re afraid of pointing out these deficiencies to your fellow scientists?

    I think you’ve missed part of the point. If the data has been aquired under a Federally funded grant, NSF, NASA, etc. If isn’t your data.

    Bob Koss:
    They have the chronologies for years without being able to come up with anything useful. But, rather than archive them and let someone with possibly a different perspective on analysis have a whack at them, they’ll sit on them.

    Per says:
    In (astro/particle)physics, there are innumerable projects where data is collected, but put in a public archive rapidly.

    A recurrent theme here: where, oh where, are thou data? First, it is no one’s job (certainly not mine) to police my peers. We are all individuals with our own reasons for doing what we do. But here on this blog one person starts the conversation with an ad hom calling me”afraid of pointing out deficiences to your fellow scientists” when the person who makes the statement has no clue what or what not I have pointed out to peers. Second, the existence of online databases and supplemental data sets as part of publications is a relatively new development in science and scientific data management. How long have the internets been around, since the early 90s? Many journals that I am familiar with do not, in fact, have any capability at present for managing supplemental data. The ITRDB has been online only since about 1995. Before that since about the mid-1970s it was available on floppies but, of course, updating as new data were submitted was a bit problematic. And Per, please list some of these public archives from astro/particle physics that you appear to know so well. I just Googled “astroparticle physics public data archives” and the third link (the first was a PDF and the second a PS file) was an article from the CERN Courier (2007, Vol 47, No 3) entitled: “Let the data free! Three researchers working in the new field of astroparticle physics argue the case for making the data from astroparticle experiments public?. Sounds to me like they are having some issues with data access as well. Should there be better data access? Most certainly, and personally I have been and am helping in that regard in my own little corner of the world. But this strawman set up initially by Mr. McIntyre and repeated ad infinitum on this blog is certainly getting old.

    Finally, they ARE my data. Funding agencies pay me for my expertise, my imagination, and my insights to be able to make some advance in our understanding of how nature works, not for raw data sets. Our society has made a commitment to supporting science in the form of funding researchers to do what they do best as determined from their education, experience, and academic achievements. Quite often scientific investigations lead to dead ends, science is not done by recipe, and often data are used to address more than one hypothesis. It is the understanding and inferences supplied by the scientist that funding agencies are interested in, not her or his raw data. As for NSF data archival requirements, from what I understand there are no hard and fast rules as to what data are to be archived: for example, in dendroclimatology, raw data in the form of ring widths are not requested or required, only the final reconstruction.
    Peter Brown
    Apr 1, 7:49 AM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    In response to several requests, I started to try to address some of the science issues that Willis Eschenback asked back in #13. However, just checking up again on the thread after doing some chores (just mowed the grass for the first time this season, earliest date I’ve had to do that in 14 yrs in northern Colorado), I find again the thread has degenerated into name-calling as is the usual wont on this blog.

    Pat (#65), why in the world would you propose that I am indigent? Webster:”lacking food, clothing, or other necessities of life because of poverty; needy; poor; impoverished? That is not me. But perhaps you are referring to Webster’s archaic meaning:”deficient in what is requisite? If so what is it that I am deficient in that is so requisite in your opinion? I will admit to being naive about a good many things, although not the one you label me with. And perhaps I am being completely unfair in judging the entire exercise of trying to communicate by this blog by the actions of a few, but what, pray tell, is in it for anyone to try to reach out when they get hit with inaccurate, unfair, and down-right slanderous name-calling when they try? Anyone can do that, even me: Pat, you’re ugly and your feet smell.

    Please be aware these are only one person’s opinion on these questions and so far I only got through no. 2, doubt I’ll get any farther.

    1) Are the mathematical methods used in dendroclimatological reconstructions valid? In particular, the use of novel, untested statistical methods without any attempt to mathematically justify their validity is worrisome. See, for example, this thread on variance adjustment.
    I cannot answer this question, I am not a statistician. I can say that I think your question is mostly a strawman; I cannot think of a single paper that I have read that used what I what I imagine you might refer to as a “novel, untested” method without providing justification for its use. Often this justification comes in the form of reference to existing literature, but it is always there. If you have a specific example, please provide one.

    One point on this question, however: mathematical and statistical models are not the beginning of dendroclimatological research. Dendroclimatology starts with mechanistic models of how trees grow and how climate affects soil and atmospheric conditions that in turn affect growth. It appears that a number of folks here have read Fritts, who is an excellent place to start. There are a combination of “top-down and bottom-up” approaches to our understanding of how climate affects growth; top-down approaches are primarily correlational (general growth patterns such as total ring width with long-term instrumental data) while bottom-up would be reductionist in approach, trying to better understand mechanistic details. Most of the conversations on this blog are only concerned with the former but it appears to me that many of the answers lie in better understanding of the latter. A third approach is simulation modeling, and there was a recent book and excellent synthesis of a number of these studies by Vaganov, Shashkin and Hughes.

    2) Are proxy reconstructions without ex ante proxy selection rules valid? And if so, what protection is there against “data snooping” and “cherry picking”?

    Trees respond to all sorts of climatological and ecological factors throughout their lives (which can, of course, be quite long). Occasionally one climatological factor is very much dominant. For example, Douglas-fir trees growing on a rocky steep slope at a dry site in northern Arizona may exhibit upwards of .7-.8 adjusted R^2 in a simple linear regression model with a seasonal or annual total of monthly precipitation data from a nearby climate station. So even in the driest of dry sites, precipitation totals do not explain all the variance in annual growth. Part of it is temperature (a hotter summer will dry the soil out faster than a relatively cooler one given the same amount of annual ppt), part of it is that monthly ppt may not be a good reflection of the actual moisture the tree sees (does all of it come in one or two thunderstorms in which most runs off or does it come in a steady soaking drizzle), part of it is the fact that the station where the instrumental data come from is over the hill (or well far away from where the trees are growing) and ppt is often very spatially heterogeneous (especially in the SW where thunderstorms may provide a good portion of the annual total), part of it are the results of ecological disturbances that affected trees individualistically or occasionally as a group, part of it are genotype differences within the stand, and part of it is simply not being able to capture in any sort of digital format the variance present within living organisms.

    Concerning site selection, generally there is some sort of ex ante expectation of what a particular site and species will show in its growth response to climate. One selects dry sites looking for drought-stressed trees, one selects upper elevation or upper latitude sites looking for temperature-stressed trees. However, in many cases it is not at all a simple response, and if you are at all familiar with the dendro literature you will have come across response function graphs. These are exploratory devices to assess not only the strength and type of principle climate response of a chronology or set of chronologies but also how well the available instrumental data sets may be used to resolve it. Coming back to the SW Douglas-fir, we find that the instrumental data may explain e.g. 70% of the variance in a ring-width series, but if one regresses that same station data against other stations in the region (and in N. AZ they can be quite far apart) one may find a comparable number.

    Also, especially with temperature, it is not simple at all what the trees are responding to vs. what data are available from a climate station. Generally it is average temperature over the growing season, but this again only explains so much of the variance in the tree growth. The tree may be responding to combinations of growing season length, dates of first and last frosts, etc, but all we have to work with may be monthly (occasionally daily) data sets of min, max, and avg temps, often with missing values, often from stations located in the cold sink in the valley below that are seeing quite different temperature regimes than the trees on the ridge above. And even if one finds a dominant pattern affecting growth (e.g., annual ppt coming back to the SW example) there are often other significant relationships as well. For example, in very dry SW sites, one often finds a negative response to summer temperatures, the hotter the summer the faster the soil dries out and the slower the growth. Thus there is also information on temperature contained within the chronology, but generally the most parsimonious model is selected (i.e., ppt).
    Peter Brown
    Apr 1, 3:52 PM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    “Novel, untested” method? Try Mann, Bradley, Hughes 1998. The novel, untested method: principle components analysis.

    PCA was used in time series analysis before MBH; perhaps you refer to its use in dendroclimate data, John A.? If those are your criteria for “novel, untested”, then how would science proceed if it did not apply new methods for analyzing data?
    Apr 1, 4:53 PM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    Oh, thank you! That clears up the comment considerably. I take back my name-calling of Pat, he is not ugly and his feet don’t smell. Pat, I apologize. Although I really would not characterize myself as indignant; more curious to see where this all goes.
    Apr 1, 5:13 PM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    I apologize for not continuing before now to some of the science issues that Willis Eschenback asked back in #13. Here is the rest of a short answer to his question no. 2:.

    2) Are proxy reconstructions without ex ante proxy selection rules valid? And if so, what protection is there against “data snooping: and “cherry picking”

    Returning to the SW Douglas-fir example: recall that annual ppt over the 20th century instrumental period explains perhaps 70% of the variance in the ring-width chronology for the same period in a simple linear regression. However, as I mentioned in the previous post, response function analysis shows that there is also a much weaker but still significant inverse response to summer temperatures, explaining perhaps only as much as 10% of the remaining variance (As for the rest, who knows? All those other factors – and others – that I listed in the previous post. Please keep in mind these are only statistical models.). Thus that chronology could be used – albeit with much less confidence – to also examine temperature variations.

    This is the basis for using networks of tree-ring chronologies in reconstructing broad-scale patterns of temperature from otherwise drought-sensitive trees. There is almost always some temperature response in the individual sites, and typically some sort of chronology selection process is used to select them to maximize both the individual and well as collective response. A regional (or inter-hemispheric) network would necessarily be compared against regional (or inter-hemispheric) instrumental data to develop statistical models describing the relationship in some sort of objective manner. And I would suggest starting off with Fritts’ 1991 book if you’ve not read that; this has much more detail about the justification for using such a approach on a 65 site network across western NA in the first study of its kind (he developed both temp and ppt reconstructions back to 1600).

    Now, whether one calls the process of chronology selection for such broad-scale studies “cherry picking” or “data snooping”? I suppose would be in respect to one’s preconceptions and biases against the entire process in the first place. All scientific studies begin with premises that guide model and data selection. So in answer to the second part of your question above, the premise of the question is incorrect; there is no need for “protection” since those terms are irrelevant to the process of development of explicit site selection criteria.

    3) Many proxy temperature reconstruction use proxies which have been used previously for proxy precipitation reconstructions. What methods (if any) have been used to control for the other variables? If there is no attempt made to control for confounding variables, is the study valid?

    I am not the person to answer this question. I would suggest that the main approach, as I see it, has been blunt force, the law of large numbers; with enough chronologies that have weak temperature response (and again in ppt-sensitive series this is typically an inverse response) the broader-scale patterns will emerge and be strengthened. It is analogous of course to trying to see global warming in a single time series, can’t be done. (And to the commenter in post #85 about my observation of early grass-cutting in Colorado, did I say anything about it being a sign of global warming? Simply an observation” please don’t place your biases into my comments, you sanctimonious SOB.)

    4) Temperatures which are too hot or too cold both cause narrow tree rings. Under the assumption of linearity in proxy reconstructions, this means that hot times will be interpreted as cold times. Why is this ignored in temperature reconstructions? At a minimum, it should make for asymmetrical error estimates, but I have never seen even that done, much less any serious discussion of the inherent problems.

    This is not ignored in temperature reconstructions, this is an active area of research (e.g., see the recent review by D’Arrigo, Wilson, et al.). The so-called “divergence problem” is a big area of concern, not only for what it means to current tree growth and forest patterns (and indirectly to a host of other issues in forestry, such as widespread and apparently unprecedented bark beetle and other insect outbreaks) but what that does mean for climate reconstructions. In the absence of other evidence, we must assume uniformitarianism in climate/growth response. For example, in our northern Rockies work (Mr. McIntyre’s comments on which started my responses to this blog) one approach we are looking at is to use multiple proxies (ring width and max latewood density) and multiple spp to see how different the later 20th century may be in relation to the rest of the records. Do we need to do more? Absolutely, and two approaches I feel we need more of are mechanistic and experimental studies and simulation modeling (which there is a lot of work being done in the latter).

    5) Are proxy reconstructions which do not have a validation period, but only a calibration period, scientifically defensible?

    Why not, dendroclimatology is the only discipline that I am aware of that routinely does any sort of calibration/verification process. Validation of a reconstruction may be done through comparison of other reconstructions, historic records, etc, to provide some idea of how well it compares to historical understanding.

    6) How can proxies which do not correlate with local temperatures be used as a proxies for global temperatures?

    Several of our higher elevation chronologies from here in CO correlate quite poorly with nearby climate stations (for example, check out Lexan Ck with Fraser, CO, temps) because of what I mentioned already, the climate station is down in the cold sink (Fraser’s motto is the icebox of the nation) while the trees are high up on the ridge above. The trees correlate much better with regional temp averages (e.g., the CRU gridded data) because temp tends to be more spatially autocorrelated than ppt and the regional averages reduce the effects of individual station anomalies. Global temps would be the next step up.

    7) Fritts divides sites into”complacent” and “sensitive”, depending on whether they respond to a given signal (temperature, precipitation, etc.). However, even within “sensitive” sites, there are trees which respond and trees which don’t, and no one seems to know why. This raises questions, including:

    First, your premise is generally incorrect in that “no one seems to know why”. In chronologies that I am familiar with one measure we use to assess in-common patterns between trees is the inter-series correlation. Often there may in fact be one to a few trees that have lower inter-series r than the rest, but usually this is can be explained by microsite variations. For example, in ppt-sensitive sites, the poorer correlating series may have come from trees that were growing in a spot with better soil development or off the top of the ridge where wind did not dry the soil out as rapidly, etc. So I would suggest that in many cases lower correlations can be explained by ecological factors.

    a) Does a site remain “complacent” or “sensitive” over a period of centuries, or can it be sensitive for a while and then become complacent?

    This can be tested for by running correlations, variances, or other measures of time series characteristics. Occasionally the early growth of a tree does not appear to be responding to climate as older trees nearby; this is likely due to growing conditions in the younger tree (e.g., competition with neighbors until it reaches the canopy). In this case, a common remedy is to remove the early growth from the series. However, I have run evolutive analyses on a number of chronologies and have never found any significant deviations over the length of the series.
    b) If a site is “sensitive” to temperature due to it being close to the treeline, will it stay “sensitive” when the treeline changes? And if so, will the “sensitivity” change?
    Good question; in our treeline sites in CO we appear to have had a treeline shift about 1250 CE; growth was very restricted before this and lots of reaction wood, which both imply Krumholtz growth forms, followed by a growth release and more regular and concentric growth after ~1250. Also a lot of trees in the stand appear to have started up about that time. Treeline today is about 50 m above this stand. However, this I suggest is a different scenario than if one is dealing with an existing stand of trees already established as trees, and again one method to test if there are possible changes in response would be to do some evolutive analyses over the length of the series to test for changes.

    c) If a site is “sensitive” at a given average temperature, will it remain “sensitive” if the average temperature rises? If it falls?

    Likely in a general fashion, assuming there is a linear response to temperature. From a purely practical standpoint an assumption in dendroclimatology is that of growth limiting factors; to reconstruct climate one assumes that a single factor is limiting to tree growth. However, obviously, this is not always the case. There likely is a low point in temp when a tree may be extremely responsive to it as limiting factor, an optimal range when the tree could care less, and a high point when some other limiting factor (e.g., soil moisture) may be the limiting factor. I’m sure you realize this already, but any type of statistical model that may be developed from such relationships does have confidence intervals associated with it.
    Apr 2, 6:28 AM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    In #88, Pete, a quick response to just the first part of your response to my comment: Thank you for the links. I’ve not had a chance to explore these at all, but just quick browses of a few suggests to me that these are mainly databases maintained for individual projects, not for public data repository (and I may be completely incorrect in that observation, but in my quick perusal I did not see any sort of submission page, e.g., similar to that of the ITRDB. Just one quick quote from the TRACE site:

    An Open Letter to the Solar Physics Community on TRACE DATA Access
    One feature of the TRACE mission is the open data policy. The purpose of this letter is to clarify this policy and to encourage a dialog on how to insure its fair and reasonable implementation.
    Our fundamental data policy is simple: All TRACE data will be equally available to everyone on the World Wide Web. An open data policy is an experiment for Solar Physics space experiments. There will be misunderstandings that cause varying degrees of unhappiness. There is no perfect policy and it is naive to expect that deviations from established practice will not result in some problems.

    Again this is just a very quick perusal on my part (5 minutes) and in that time I came across this statement that this is an “experiment” in open data. So perhaps many disciplines are in the same boat with regards to making sure data are accesible?
    And BTW, the quote of mine you highlight above was by no means”cherry-picking” (appears to be one of the favorite phrases on this blog, cherry-picking this, cherry-picking that), it was completely and utterly random (as random as Google can be), it was, as I already stated, the first real link I came to in a Google search. How in the world is that”cherry-picking”?
    Apr 2, 6:55 AM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    Re 26:

    However, what happens with someone like Peter Brown – and we’ve seen this before – is that when there’s a flood of comments, they pick and choose what they reply to and will generally pick the most political and/or the weakest comment to respond to and give the appearance of being responsive without engaging on more challenging questions.

    Mr. McIntyre; FYI I’ve just provided a continuation of my responses to the questions that Mr. Eschenbach asked in post #13 on the other thread. I will keep any substantiative comments there since that is where you first highlighted research that I am involved in. I would ask which is the most political or weakest comments that I have responded to so far in your opinion, and which are the most challengening that I have not (please do so on that thread). As for picking and choosing, I would hope that an objective observer on this blog would realize that most of comments are simple flames and/or ad-homs, or otherwise add nothing to any sort of discussion. Many posters are simply trying to be provocative. And please be aware I have already stated that I am not a statistician, and would not be able to address any questions of your’s or others on the MBH reconstruction, which appears to be the recurrent theme. That is not trying to pick and choose your questions to answer, simply that scientists do have different areas of expertise.
    Peter Brown
    Apr 2, 7:21 AM ” [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

    Re #26 again: Also please be aware that while this exercise has been interesting to me over the weekend, I will be in conferences most of this week (after Tues) and next and likely won’t have much of a chance to respond to anything during that time. Again, I would prefer any major questions to be posted to the other thread; that is another difficulty with trying to carry on any conversation on a blog, it moves along rather quickly.
    Apr 2, 7:31 AM [ Edit | Delete | Unapprove | Approve | Spam | View Post ]

  9. Steve McIntyre
    Posted Apr 3, 2007 at 9:21 AM | Permalink

    In keeping with my undertaking not to argue points on this thread, I note that I’ve posted up a response on another thread to the claim:

    And, finally Steve M, though you are more civil than most here, you cherry-pick pretty well in making your arguments. One case in point – the quotes you copied from the discussion on the dendro listserv.

  10. Steve McIntyre
    Posted Apr 3, 2007 at 9:30 AM | Permalink

    Martin Wilmking has added here

    #50 Steve, yes, i agree. it is fair to say that you did report on our work. and i am convinced that you would also report on it in the future, if we had addressed several of the problems and would come up with support for the hockey team. lets keep this as fair as possible…

    #49 at least at some northern treeline sites, as well as some altitudinal treeline sites, stems are conserved standing or lying due to the either very cold or very dry conditions. thats where a lot of the dead material for chronologies comes from. i agree that in other cases, the evidence might be lost, as i stated above.
    Apr 3, 8:37 AM ‘€”

  11. Steve McIntyre
    Posted Apr 4, 2007 at 3:37 PM | Permalink

    Nordic writes in another thread:

    The Cedar Breaks site in particular is very close to where I live and work. I did quite a bit of work with Picea engelmannii in the stands just to the east of Cedar Breaks about 10 years ago (major D. rufipennis outbreak). Some of the stands I inventoried were within half a mile of the rim, but I can’t imagine any of those trees giving a good temperature signal. Most of the spruce within Cedar breaks itself (IIRC) grow either along the rim which slopes away to the east, or on the steep slopes of the Breaks which fall away to the west with some south and north exposures – the spruce would tend to grow on the north-facing slopes of the breaks where soil conditions are cooler and more mesic. All of the potential growing sites for spruce would be subject to periodic drougths. Winter precipitation in that area, which is critical for earlywood development can vary widely from year to year.

  12. Steve Sadlov
    Posted Apr 4, 2007 at 4:00 PM | Permalink

    RE: #16 – Just like in the White Mountains. Earlywood development in many years, and I would imagine, even latewood development in years with a weak Monsoon, will depend on snow pack moisture content and persistence. This year is a good example of a year in which there will be immense moisture stress, barring a near record Monsoon. Due to the dry, cold and windy conditions this past winter, the snow pack is really hurting. Those BCPs are going to be bumming out this summer.

  13. Nordic
    Posted Apr 4, 2007 at 11:17 PM | Permalink

    RE: #17: Here is the water year data for Webster Flat – a SNOTEL station located near Cedar Breaks.
    It looks like many of the conditions you describe apply for the White Mountains apply there as well. Ironically, this was supposed to be a wet winter. The El Nino conditions were supposed to bless us with a warm southwest flow like we had all winter in the 2005 year.

    Note: See the big jump in precipitation and snowpack at the beginning of Jan 2006 (2005 water year)? That’s the storm I drove 120 miles through in order to be at my son’s birth. Luckily my wife was already up north staying with her aunt 2 miles from the hospital!

  14. Steve McIntyre
    Posted Apr 5, 2007 at 7:57 AM | Permalink

    Scott Saleska of the University of Arizona, one of the climate scientists who filed the Amicus Curiae in the recent Mass vs EPA writes on another thread,

    Though I haven’t so far worked in the climate proxy field, I basically see what you are trying to do here as scientific in a fundamental sense: evidence based inquiry, without accepting the say-so of anybody no matter their authority.

    Whenever I look at this site … I am reminded of the saying that I think I first saw on the Splus news list: “In god we trust, all others must bring data.”) CA certainly is more scientific in terms of representing the actual ongoing (sometimes messy) process of ongoing evidence-based inquiry than any blog I am aware of. I read your GRL paper when published, thought it a reasonable criticism at the time, and noted that the NAS report did basically endorse it.

  15. twq
    Posted Apr 8, 2007 at 2:53 PM | Permalink

    [snip- I’ve moved this comment to another thread as this is reserved for dendroclimatologist comments.]

  16. twq
    Posted Apr 9, 2007 at 2:09 AM | Permalink

    In this special area (extremely cold, dry, and terrain units), the mechanism is very complex. I forgot saying one study paper in Chinese. This paper describes one of mechanism that tree ring widths record temperature change in this area. . Since it is written in Chinese, I don’t want to report here more profound knowledge. Do you have any mecharnism for your allegation that ring width is an indicator of precipitation? I am all ears.

  17. twq
    Posted Apr 9, 2007 at 3:16 AM | Permalink

    Re: If you say that the work that uses Qilianshan junipers as a temperature proxy is “less-respected” than others, then I presume that such work should not be relied upon in IPCC 4AR or that appropriate asterisks should be placed in IPCC 4AR. I listed the following studies that used Qilianshan junipers directly or indirectly: Crowley and Lowery 2000, Mann and Jones 2003, Moberg et al 2005, Hegerl et al 2006, Osborn and Briffa 2006. All of these studies are cited favorably in IPCC 4AR. I did not comment on the motives of the IPCC 4AR authors, but, if, as you say, these studies are “less-respected”, that should have been mentioned in an assessment report.

    Like I said in another thread, at this stage, it is still open whether the ring widths represent temperature or precpitation. Why are you so sure that it is an indicator of precipitation? Have you done original investagation? I guess you do not. However, in this thread, you are so certain that the ring width should represent precipitation change. It si real condition? I guess you are also not for sure. But why you are so adamnant? My suggestion is that we should do further investagation when we make final conclusion. do you agree? What I said last time is remove here moved to anhother thread. I hope you kindly keep it here this time. I hope anyone who is cocerned with ring widths have the reight to discern the truth, not just believe your allegations. thank you.

    I have clearly reported that the ring widths have significant correlation with both temperature (winter temperature and autumn temperature) and precipitation (spring) during the last 50 years. Thus, at this stage, it can be served as both temperature and precipitation proxies before its growing mechanism is observed and investigated. In other words, it is not clear if it is better for temperature and precipitation. We should note that any certain allegation for its representativity for temperature, precipitation or other indices needs further investigation. I have listed some papers in this area, in which the ring widths are used as temperature reconstruction rather than precipitation. Is it really unclear for you (steve and your supportors)? I am very confusing about your position. I repeat and suggest you should re-examine what I listed before in this thread, then we continue the next step for discussion. Otherwise, we have no basis for further discussion. On the other hand, I should have previledge for saying its representative because I have been to this study area (Qilianshan and its adjoining area) more than hurdred of times, but for you, just get knowledge from the text. I am sure that knowledge comes from practice. Except that you can report further knowledge (such as its mechanism), it is futile for me accepting your allegation.

  18. Paul Linsay
    Posted Apr 9, 2007 at 6:19 AM | Permalink


    …ring widths have significant correlation with both temperature (winter temperature and autumn temperature)…

    ?Please explain how trees grow in winter and autumn?

  19. Steve McIntyre
    Posted Apr 9, 2007 at 6:38 AM | Permalink

    Do you have any mecharnism for your allegation that ring width is an indicator of precipitation? I am all ears.

    twq, I would urge you to read any dendro text, e.g. Fritts 1976, where the connection between ring width and precipitation. twq, you have not identified yourself as a dendroclimatologist and your comments suggest that you aren’t one. I wish to reserve this thread for dendroclimatologists. That is the reason why I moved your comments on this thread to another thread and will do so in the future. You are welcome to discuss these matters on another thread.

    The specialist literature on Dulan junipers states that the ring widths that they sampled were correlated to precipitation and proposed precipitation reconstructions based on these studies. The following literature is a sample (and includes both Chinese and Western scientists):

    Shao, X.M., Huang, L., Liu, H.B., Liang, E.Y., Fang, X.Q., Wang, L.L., 2004. Reconstruction of precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai. Science in China (Series D) 34, 145’€”153.

    XUEMEI SHAO, ERYUAN LIANG, LEI HUANG AND LILY WANG, A 1437-year Precipitation History From Qilian Juniper in the Northeastern Qinghai-Tibetan Plateau

    Zhang, Q.-B., Cheng, G., Yao, T., Kang, X. and Huang, J., 2003: A 2,326-year tree-ring record of climate variability on the northeastern Qinghai-Tibetan Plateau. Geophysical Research Letters, Vol. 30(14), 1739, doi: 10.1029/2003GL017425.

    Zhang et al 2007 A millennium-long tree-ring chronology of Sabina przewalskii on northeastern Qinghai-Tibetan Plateau, Dendrochronlogia 24

    SHEPPARD P. R. (1) ; TARASOV P. E. (2) ; GRAUMLICH L. J. (1) ; HEUSSNER K.-U. (3) ; WAGNER M. (3) ; ÖSTERLE H. (4) ; THOMPSON L. G. (5) ; 2004. Annual precipitation since 515 BC reconstructed from living and fossil juniper growth of northeastern Qinghai Province, China, Climate dynamics, 23,. 869-881

    Shao, Xuemei, Lei Huang*, Xiuqi Fang’€ *, *, Lili Wang*, JunboWang*, Haifeng Zhu, A Dendroclimatic Study of Qilian Juniper in the northeast Qinghai-Xizang (Tibet) Plateau, downloaded ~2003.

    Sheppard et al for example say:

    On the monthly scale, winter’€”spring precipitation correlates mostly positively with tree growth while winter’€”spring temperature correlates negatively (Fig. 4). For precipitation, the full water-year from previous July through current June correlates the strongest as a single season with a value of +0.70. For temperature, April through June correlates the strongest as a single season with a value of 0.42. These results combine to indicate that pre-growing season moisture availability is the most important factor limiting tree growth at these juniper stands, with precipitation of the entire year of previous July through current June being the critical weather variable affecting soil moisture availability. This finding is consistent with other well-replicated juniper sites in the region (Zhang and Wu 1992), with sites farther away such as to the east in the Qinling Mountains (Wu 1994) and to the north in Mongolia (Jacoby et al.1999 with sites of juniper and pines in other semiarid sites (e.g., Schulman 1956; Grissino-Mayer et al. 1997). This full water-year precipitation model differs from that reported by an independent dendroclimatic analysis of similar (although shorter in time) data from Dulan that concluded that the May’€”June precipitation was the main factor controlling juniper growth in the area, with a correlation value of +0.58 (Zhang et al. 2003).

    If a dendroclimatologist is going to take the trouble to assert on this board that specialist literature indicated that Meko’s Alberta white spruce are a precipitation proxy and they should not be used in a temperature reconstruction – even in the conditional of my post -, I observed that specialist literature also stated that Dulan juniper were a precipitation proxy and that they should spend energy criticizing its use in multiproxy reconstructions.

  20. Hans Erren
    Posted Apr 9, 2007 at 6:46 AM | Permalink

    re 18:
    Severe frost can damage buds, yielding narrow tree rings in the subsequent growth season.

  21. twq
    Posted Apr 9, 2007 at 7:05 AM | Permalink

    Thank you. Twenties years ago, I finished reading Fritts book. So I suggest you should read it carefully to see why ring widths have good correlation with winter temperature.

  22. twq
    Posted Apr 9, 2007 at 7:09 AM | Permalink

    Re: #17

    I have made explanations about it in so called ‘Dendro truth squad’. Would you please read it?

    Rapid tree growth with respect to the last 400 years in response to climate warming, northeastern Tibetan Plateau (p n/a)
    Xiaohua Gou, Fahu Chen, Gordon Jacoby, Edward Cook, Meixue Yang, Jianfeng Peng, Yong Zhang
    Published Online: 25 Jan 2007
    DOI: 10.1002/joc.1480
    Abstract | References | Full Text: PDF (Size: 244K)

    I suggest you consult Fritts HC (1976) and Kimmins (1987), and many papers. It is easier to understand for dendrochronologists. Here I’d like to add some sentences (Gou et al. 2007). For the Tibetan Plateau with a special terrain, if the previous winter temperature is very low, the annually frozen soil layer could be thicker and the thawing time could be delayed in the coming spring. Thus tree growth would be negatively affected adn the tree-ring width of the year after a cold winter could be narrower. Therefore the correlation between tree ring width and winter temperature is reasonable, based on inferences from known physiological processes. For more thoughtful discussion see the below referneces. This is also my final reply.

    Kimmins J P. Forest Ecology. New York: Macmillan Publishing
    Company, 1987. 1~531
    Fritts H C. Tree ring and climate. London: Academic Press,
    1976. 1~567

  23. twq
    Posted Apr 9, 2007 at 12:48 PM | Permalink

    Re #19,

    twq, I would urge you to read any dendro text, e.g. Fritts 1976, where the connection between ring width and precipitation. twq, you have not identified yourself as a dendroclimatologist and your comments suggest that you aren’t one. I wish to reserve this thread for dendroclimatologists. That is the reason why I moved your comments on this thread to another thread and will do so in the future. You are welcome to discuss these matters on another thread.

    Are you surely a dendroclimatologist? It seems that you are dendroclimatologist, ice core climatologist, marine sediment climatologist, climatologist, economist, et al.

  24. bender
    Posted Apr 9, 2007 at 1:24 PM | Permalink

    So tempting to reply. Must … self-police …

  25. bender
    Posted Apr 9, 2007 at 7:24 PM | Permalink

    Re #22

    Rapid tree growth with respect to the last 400 years in response to climate warming, northeastern Tibetan Plateau
    Xiaohua Gou, Fahu Chen, Gordon Jacoby, Edward Cook, Meixue Yang, Jianfeng Peng, Yong Zhang
    Published Online: 25 Jan 2007

    Please, what journal title, volume, and page number?

  26. Steve McIntyre
    Posted Apr 9, 2007 at 10:13 PM | Permalink

    bender – I presume that it is: Gou et al, 2006, A comparison of tree ring records and glacier variations, Annals of Glaciology 43, 86-90, which has the same roster of authors in the same order.

  27. twq
    Posted Apr 10, 2007 at 1:18 AM | Permalink

    Dear bender,

    This is

    Gou Xiaohua, et al., 2007. Rapid tree growth with respect to the last 400 years in response to climate warming, northeastern Tibetan Plateau. International Journal of climatology. Published online in Wiley InterScience, DOI: 10.1002/joc.1480.

    You can download it from the website

    You will find it. This study area discussed in this paper is also located in NE tibetan Plateau, but is also sensitive to winter temperature change. Especially, in the low-frequency domain, there is good agreement with Qilianshan ring widths, which is consistent with conclusions derived by Liu et al. (2006), Kang et al., (1997), and Shao et al., (2004) who suggested that the Qilianshan ring widths has good correlation with temperature change.

  28. bender
    Posted Apr 10, 2007 at 6:40 AM | Permalink

    Thanks twq, for the reference. But for 25$?! I don’t think so! Why don’t you email a pdf copy to Steve M so that he can read it? I doubt he’ll want to pay 25$.

  29. bender
    Posted Apr 10, 2007 at 6:59 AM | Permalink

    twq, Gou et al (2007) is not even available in print yet. Int. J. Climatol. is currently on Vol. 27(2). Let us know when you’ve got a volume, issue and page number.

  30. Steve McIntyre
    Posted Apr 10, 2007 at 7:41 AM | Permalink

    If you google: “Gou Xiaohua, et al., 2007. Rapid tree growth with respect to the last 400 years in response to climate warming, northeastern Tibetan Plateau. International Journal of climatology” guess what you get?

  31. Steve McIntyre
    Posted Apr 10, 2007 at 8:15 AM | Permalink

    CA readers have now sent me both Gou et al 2006 and Gou et al 2007, which I will be discussing fairly soon.

  32. jae
    Posted Apr 10, 2007 at 5:17 PM | Permalink

    30: I googled it and got nowhere. The link goes to an old article by other researchers. I did notice that some of the Team seem to be co-authors.

  33. bump
    Posted Apr 17, 2007 at 1:29 PM | Permalink

    Rather quiet from Rob Wilson et al.

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